Swift: RegEx not returning expected results

Question

Let me preface this with I am pretty noob at doing regex. The code I am writing is for macOS, not iOS but I don't think that matters in this case. I'm trying to search a git diff return based on the change range indicators. Here's is the content I am searching (the variable is called element):

3b8d5178f4d21e9269547e8f0bae4b7daa7d8206
Author: Steve <[email protected]>
Date:   Fri Oct 4 16:55:50 2019 -0400

    Fixed responsiveness of code blocks

diff --git a/examples/video/outstream/pb-ve-outstream-no-server.html b/examples/video/outstream/pb-ve-outstream-no-server.html
index ae813578..e18e31ec 100644
--- a/examples/video/outstream/pb-ve-outstream-no-server.html
+++ b/examples/video/outstream/pb-ve-outstream-no-server.html
@@ -24,7 +24,7 @@ sidebarType: 4

        <div>

-           <div>
+           <div style="width:60vw;">

                <p>Lorem ipsum dolor sit ....</p>
            </div>
@@ -33,7 +33,7 @@ sidebarType: 4
                <p>Prebid Outstream Video Ad</p>
             </div>

-           <div>
+           <div style="width:60vw;">
                <p>Sed ut perspiciatis ...</p>
             </div>
        </div>          
@@ -49,9 +49,9 @@ sidebarType: 4
            Do not forget to exchange the placementId in the code examples with your own placementId!</p>
        </div>

-       <div>
+       <div style="width:60vw;">
            <h4>Place this code in the page header.</h4>
-<pre class="pb-code-hl">
+<pre class="pb-code-hl" style="width:60vw;">
 <!--put javascript code here-->
 &lt;script&gt;
     var pbjs = pbjs || {};
@@ -95,9 +95,9 @@ sidebarType: 4
        </div>

        <!--body code example-->
-       <div>
+       <div style="width:60vw;">
            <h4>Place this code in the page body.</h4>
-<pre class="pb-code-hl">
+<pre class="pb-code-hl" style="width:60vw;">
 <!--put body html and javascript here-->
 &lt;div id='video1'&gt;
    &lt;p&gt;Prebid Outstream Video Ad&lt;/p&gt;

here's my regex to get the change indicators

 do {
     let regex = try NSRegularExpression(pattern: "@@ (.*) @@", options: .caseInsensitive)
     let matches = regex.matches(in: element, options:[], range: NSRange(location: 0, length: element.utf16.count))

     for match in matches {
         let strElement = element as NSString
         arrMatches.append(strElement.substring(with: match.range) as String)

     }
 } catch {
     print ("Error with regex return")
 }

Works as expected, I get all four instances:

["@@ -24,7 +24,7 @@", "@@ -33,7 +33,7 @@", "@@ -49,9 +49,9 @@", "@@ -95,9 +95,9 @@"]

I now want to capture the changes between the indicators. But I am not getting any results, not even an error on the catch. Here's a hard coded example of what I am trying to do:

do {
   let regex = try NSRegularExpression(pattern: "@@ -24,7 +24,7 @@ (.*) @@ -33,7 +33,7 @@", options: .caseInsensitive)
   let matches = regex.matches(in: element, options:[], range: NSRange(location: 0, length: element.utf16.count))
   print(matches.count)//<--prints 0, expecting 1                  
   for match in matches {
      let strElement = element as NSString
      print(":::" + strElement.substring(with: match.range) as String) //<--Nothing prints
   }
 } catch {
      print ("Error with regex return")//<-but nothing prints here either...
 }

The content has a lot of tabs and linebreaks so I am wondering if I somehow have to account for those within my regex? Any help would be appreciated.

I should get 4 results, the first result should be:

sidebarType: 4

        <div>

-           <div>
+           <div style="width:60vw;">

                <p>Lorem ipsum dolor sit ....</p>
            </div>

the second result would be content between change indicator 2 and 3, the third content between 3 and 4 and the last all content after 4

If you plan to get some text between the two substrings, @@ -24,7 +24,7 @@ and @@ -33,7 +33,7 @@, use "(?s)@@ -24,7 \\+24,7 @@(.*)@@ -33,7 \\+33,7 @@" — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Nov 19, 2019 at 14:05
@WiktorStribiżew - That was it. Thank you. Make it an answer and I'll accept it! — PruitIgoe
– PruitIgoe, Commented Nov 19, 2019 at 14:10

Wiktor Stribiżew · Accepted Answer · 2019-11-19 14:13:50Z

You may use

(?s)@@(?:\s+[-+]?\d+(?:,\d+)?){2}\s+@@(.*?)(?=@@(?:\s+[-+]?\d+(?:,\d+)?){2}\s+@@|\z)

Get the Group 1 value using strElement.substring(with: match.range(at: 1)) as String).

See the regex demo

See the Swift code demo:

let element="3b8d5178f4d21e9269547e8f0bae4b7daa7d8206\nAuthor: Steve <[email protected]>\nDate:   Fri Oct 4 16:55:50 2019 -0400\n\n    Fixed responsiveness of code blocks\n\ndiff --git a/examples/video/outstream/pb-ve-outstream-no-server.html b/examples/video/outstream/pb-ve-outstream-no-server.html\nindex ae813578..e18e31ec 100644\n--- a/examples/video/outstream/pb-ve-outstream-no-server.html\n+++ b/examples/video/outstream/pb-ve-outstream-no-server.html\n@@ -24,7 +24,7 @@ sidebarType: 4\n\n        <div>\n\n-           <div>\n+           <div style=\"width:60vw;\">\n\n                <p>Lorem ipsum dolor sit ....</p>\n            </div>\n@@ -33,7 +33,7 @@ sidebarType: 4\n                <p>Prebid Outstream Video Ad</p>\n             </div>\n\n-           <div>\n+           <div style=\"width:60vw;\">\n                <p>Sed ut perspiciatis ...</p>\n             </div>\n        </div>          \n@@ -49,9 +49,9 @@ sidebarType: 4\n            Do not forget to exchange the placementId in the code examples with your own placementId!</p>\n        </div>\n\n-       <div>\n+       <div style=\"width:60vw;\">\n            <h4>Place this code in the page header.</h4>\n-<pre class=\"pb-code-hl\">\n+<pre class=\"pb-code-hl\" style=\"width:60vw;\">\n <!--put javascript code here-->\n &lt;script&gt;\n     var pbjs = pbjs || {};\n@@ -95,9 +95,9 @@ sidebarType: 4\n        </div>\n\n        <!--body code example-->\n-       <div>\n+       <div style=\"width:60vw;\">\n            <h4>Place this code in the page body.</h4>\n-<pre class=\"pb-code-hl\">\n+<pre class=\"pb-code-hl\" style=\"width:60vw;\">\n <!--put body html and javascript here-->\n &lt;div id='video1'&gt;\n    &lt;p&gt;Prebid Outstream Video Ad&lt;/p&gt;"
do {
   let del = "@@(?:\\s+[-+]?\\d+(?:,\\d+)?){2}\\s+@@"
   let regex = try NSRegularExpression(pattern: "(?s)\(del)(.*?)(?=\(del)|\\z)", options: .caseInsensitive)
   let matches = regex.matches(in: element, options:[], range: NSRange(location: 0, length: element.utf16.count))
   print(matches.count)//<--prints 0, expecting 1                  
   for match in matches {
      let strElement = element as NSString
      print(":::" + strElement.substring(with: match.range(at: 1)) as String) //<--Nothing prints
   }
 } catch {
      print ("Error with regex return")//<-but nothing prints here either...
 }

The regex is of the (?s)\(del)(.*?)(?=\(del)|\z) form:

(?s) - a DOTALL inline regex modifier
\(del) - the delimiter pattern
(.*?) - Group 1: any 0+ chars, as few as possible
(?=\(del)|\z) - right after, the must be a delimiter pattern or (|) end of string (\z).

The delimiter pattern matches

@@ - a literal string
(?:\s+[-+]?\d+(?:,\d+)?){2} - two occurrences of
- \s+ - 1+ whitespaces
- [-+]? - an optional + or -
- \d+ - 1+ digits
- (?:,\d+)? - an optional sequence of , and 1+ digits
\s+ - 1+ whitespaces
@@ - a literal string

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